Algae inside of light

[Winger 03]

Looking for some advice.....

I have a couple of PAL 2000 lights in my 19,800 gallon Fiberglass pool with a Salt Chlorine generator, one in the shallow end between 2 returns and one in the deep end just a little below the skimmer. The light has a clear lens cover that can be removed and rep;aced with colored ones if I want to change the color of the light. We never do this, but it is on the inside of the removable lens cover that I get some algae buildup.

This is our 4th year with the pool, and it has only happened the past 2 years. Also, it is only on the lens cover that is in the deep end just below the skimmer.

I tested water last night and here is what I have.....

Fc = 7
Cc = 0
pH = 7.6
TA = 70
CYA = 50
CH = 190

So my numbers look reasonable (need to bump CYA and CH just a bit), yet I still get a little algae in the light cover. My guess is that the circulation inside the cover is not too great and maybe I can drill some holes to improve that. But..... how come i do not have algae in both lights?

I am stumped.

 

[Bama Rambler]

It could be that the other light either leaks a little more water into it, and/or the circulation by it is a bit better than other one. One could also see more sun than the other. I'd probably make it a habit to take them out a couple times a year and clean them good.

 

[Winger 03]

Sounds good Dave, glad to see that is was not really an error on my part.

 

[chem geek]

If you were able to completely get them clean, then you might not get any algae spores into them so they would remain algae free. In other words, if the circulation is very poor, then it's less likely for algae in the pool water (which should be minimal given proper chlorine levels) would get into the light and then grow. Also, if the circulation is poor, using a tiny amount of Polyquat 60 algaecide in the light might last a long time since it won't break down so quickly if chlorine isn't present.